Question

Possible Duplicate:
Casting: (NewType) vs. Object as NewType
Casting vs using the 'as' keyword in the CLR

What is the difference between these 2 types of conversion(as i’ve seen, they don’t work both all the time) :

ClassA a = (ClassA)someClassObject;

and

ClassA a = someClassObject as ClassA

Answer 1

Per http://msdn.microsoft.com/en-us/library/cscsdfbt%28v=vs.71%29.aspx (emphasis mine):

The as operator is like a cast except that it yields null on
conversion failure instead of raising an exception. More formally, an
expression of the form:

expression as type

is equivalent to:

expression is type ? (type)expression : (type)null

except that expression is evaluated only once.